DescriptionA medium-sized Phrynobatrachus with a pointed, but rounded snout and a warty skin. Males reach 25–30 mm, females 26–31 mm (SVL). The index head width/SVL is 0.24–0.29. Four warts forming two longitudinal groups of two are found at shoulder level, converging slightly towards the head. A feebly developed supratympanal fold is present. The tympanum is barely visible. Males have a single subgular vocal sac. Inactive it forms numerous folds on the throat, running either irregularly or parallel to the jaw. This feature is probably visible only during the breeding season. Feet with a small inner metatarsal tubercle. An outer metatarsal tubercle at the base of the fifth toe. Tarsal tubercle present. Webbing formula: 1 (0); 2 i/e (1–0) or (1–0.5); 3 i/e (1); 4 i/e (2); 5 (0.5) or (1). Tips of toes and fingers not enlarged. Hands not webbed; those of males bear a thenar tubercle which is enlarged at least during the breeding season.Voucher specimens: SMNS 8960 1–9; SMF 78634, 78636.The very uniform color of the dorsum is light to dark brown. Only the areas around the warts, the latter and the transversal bands on the extremities may be somewhat darker. No lateral lines. At night, some breeding males occasionally show green dorsal patches and interorbital lines. The longitudinal line on the posterior parts of the thighs is either feebly defined or absent. The vocal sac of the male is black with numerous prominent white spots. The color of female throats varies from white to white with black spots or even black. The edge of the lower jaw is spotted black. A narrow black line occasionally runs from the feebly spotted flanks to the center of the pectoral region. The rest of the venter is white.Lambiris (1989) and Passmore & Carruthers (1995) show animals with broad vertebral bands. Lamotte & Xavier (1966a) report on vaguely marbled mottled posterior parts of the thighs (sometimes irregular bordered longitudinal lines), a light interorbital line and large black dorsal blotches. In alcohol, the dorsum is uniform drab brown, and just the patches on the extremities are feebly discernible. The ventral color does not change.The voice is an amplitude modulated, very loud "craa" resembles the call of a toad. A call sequence consists of 4–230 calls and lasts about 4.6–147 sec. 1–2 calls per second are uttered. Frequency ranges from 1.2–2.3 kHz. Schiøtz (1963) describes the call as a buzzing hum which is uttered in the daytime. This observation however, rather applies to P. francisci and the sonagram he published shows a call which resembles that of P. francisci. It lasts 0.3 sec, and the dominant frequency is 1.5 kHz (Schiøtz 1964c). Van den Elzen & Kreulen (1979) give a call duration of 0.62 sec. The pauses between these calls last 0.69 sec. The dominant frequency ranges from 1.1–1.5 kHz. The sonic pressure has been measured by Passmore (1981). At a distance of 50 cm, it amounts to 104 dB. DuPreez (1996) describes the call as a vibrant ‘ghrr-uu-ghrr-uu’.A female laid 1652 eggs forming a single floating film. They were brown-white and measured 0.8–1.0 mm (egg diameter incl. jelly: 1.8–2.0 mm). The tadpoles hatched within half a day. According to Passmore & Carruthers (1995), the clutch has a diameter of 8 cm. Wager (1986) describes an egg film of 10 cm diameter, consisting of 500–800 eggs. The eggs measure 1 mm (2 mm incl. jelly). The tadpoles hatch 3–4 days later. Lambiris (1989) reports on a compact mass of 400 eggs laid in the midst of vegetation at the surface of the water. He gives the egg diameter with 1 mm (1.8 mm incl. jelly). They are light brown, with a somewhat lighter ventral side. His tadpoles hatched two days later. According to Balinsky (1969), each egg film consists of several hundred eggs. It floats at the surface, or below, the latter if the eggs stick to vegetation, and if the level of the water rises after spawning. Rose (1959) reports on 200–400 reddish-brown eggs per clutch. The eggs float on the surface. According to DuPreez (1996) a clutch comprises approx. 500 eggs. Fischer & Hinkel (1992) report on small clumps of eggs attached to aquatic plants, immediately beneath the surface.The keratodont formula of tadpoles from Comoé National Park is 1 // 1+1 / 1. The oral disc is surrounded by one lateral, and two caudal rows of papillae. The caudal one consists of very long, filiform papillae. The horny teeth are short, compact and have six tips. The larvae are nearly indistinguishable from Phrynobatrachus latifrons tadpoles.According to Lambiris (1988), tadpoles reach up to 35 mm (TL). The fin is feebly spotted, and the oral disc is surrounded lateral and caudal by papillae rows of equal length. Wager (1986) figures a larva whose body is more elongate than that of typical Phrynobatrachus tadpoles. The lateral papilla row is simple before the corners of the mouth, and double caudad of this area. All papillae are of equal length. The keratodont formula of the tadpoles is 1 / 1+1 // 2. They reach a TL of 35 mm (BL: 12 mm) and metamorphose at the age of four to five weeks (Wager 1986, DuPreez 1996). The tadpole described by Lambiris (1989), whose back, tail base and caudal bear black spots, grows as fast as the former and reaches the same length, but its keratodont formula is 1 / 2+2 // 1+1 / 2. According to Balinsky (1969), tadpoles metamorphose at the age of 27–40 days. Their development is normal at water temperatures of 21.5 to 34 °C but stagnates at lower temperatures, and the tadpoles will die when the above-mentioned level is surpassed. SVL after metamorphosis is 12.5 mm (Patterson & McLachlan 1989).

Life History, Abundance, Activity, and Special BehaviorsBoth sexes migrate to the ponds after rainfall. Males call at night from the grass on the edge of the water, or on bare ground. During the dry season, these frogs possibly live on the edges of puddles near the Kongo, a tributary of the Comoé. In March I once heard the call of this species in the day time at this site but did not succeed in locating the frogs. In the late rainy season P. natalensis starts calling regularly at dusk and continues through the night. Most choruses established along water filled car tracks without any vegetation. Here males call from the bare ground or while sitting in shallow water. Population densities were always much lower than in P. latifrons and P. francisci. P. natalensis was never observed at the respective sites during the day. According Lamotte & Xavier (1966a), just a few individuals of this nocturnal species are usually captured. According to Passmore & Carruthers (1995), P. natalensis begins to call only at 1.00 h a.m. and is heard till dawn. This observation is confirmed by Bowker & Bowker (1979), at least as far as the majority of the frogs is concerned. At the Kenyan pond observed by the latter authors, the frogs thus apparently avoided P. acridoides which called in the early evening hours. At Mporokoso, Zambia, P. natalensis began calling around 1 p.m. after heavy rain (Pickersgill pers. comm.). Perhaps calling is only restricted to certain hours were they live in sympatry with other Phrynobatrachus species. In Namibia P. natalensis calls day and night in wet weather (Channing & Griffin 1993).According to Lambiris (1988), exposed locations on the edges of the pools or plants growing in shallow water are chosen as calling sites. The frogs are usually met near open water. They are diurnal but will also call at night in periods of rainfall (Lambiris 1988b, 1989). Van den Elzen & Kreulen (1979) quote calling sites on plants, in shallow water zones and even beneath the surface. Probably they refer to a distinct cryptic species which lives in the Tanzanian upland (Pickersgill pers. comm.). In Nigeria, Walker (1968) found this species during the dry season. The frogs were usually encountered on riverbanks, i.e. far away from their savanna ponds. As he mentions neither P. francisci nor P. latifrons or P. accraensis, his statements possibly refer to one of the latter species.Inger & Marx (1961) found that this species mainly preys on terrestrial organisms. In particular, they quote beetles, termites, bugs, spiders, flies, cockroaches, orthopterans and butterflies. Termites are reported to form the bulk of the diet during the rainy season. Noble (1924) and Loveridge (1936) likewise cite termites and ants as prey.At Comoé National Park, this species is found both in larger savanna ponds harboring an abundant vegetation and in car tracks on the edges of forests which lack any trace of vegetation. This species apparently avoids closed rainforests (Noble 1924, Guibé & Lamotte 1963). Almost any type of habitat is quoted in the literature (Böhme 1994d); however, arid savannas with or without scattered trees are preferred (Mertens 1940, Perret & Mertens 1957b, Schiøtz 1964c, 1967, Broadley 1971, Lambiris 1988, Patterson & McLachlan 1989). Laurent (1979a) quotes both lowland and montane savannas. According to Lambiris (1988b) in Natal P. natalensis inhabits regions of up to 1500 m a.s.l. In South Africa, swamps and smaller temporary water bodies are colonized (Balinsky 1969, Passmore & Carruthers 1995). Smaller water bodies are also quoted by Loveridge (1933) and Fischer & Hinkel (1992). Poynton & Broadley (1985b) and Lambiris (1988) give contrary data. These authors report on permanent or semi-permanent waters. However, in the same publication they underline that these frogs prefer shallow water. Mertens (1955b) reports on animals found in a bat cave.

CommentsThis account was taken from Rödel, M.-O. (2000), Herpetofauna of West Africa vol. I. Amphibians of the West African Savanna, with kind permission from Edition Chimaira publishers, Frankfurt am Main.For references in the text, see here

Written by M.O. Roedel (roedel AT biozentrum.uri-wuerzburg.de), Post-Doc at the University of Wurzburg, Department of Animal Ecology and Tropical Biology, Wurzburg, GermanyFirst submitted 2001-05-04Edited by Arie van der Meijden (2002-01-12)